1. Field of the Invention
This invention relates, generally, to endovascular surgical tools. More particularly, it relates to a tool used in balloon angioplasty and stenting of blood vessel narrowings (stenoses).
2. Description of the Prior Art
Percutaneous angioplasty is an efficacious treatment for improving the blood carrying capacity of an artery that has become occluded by plaque, calcification, and other deposits. There are several ways of performing the procedure and the type and number of catheters and other tools used may vary between differing procedures. Typically, a needle puncture is made into an artery and an elongate guide wire is fed through the puncture site until it has traversed the stenotic lesion (the area where the plaque has built up). A guide catheter having a relatively large diameter is then introduced into the artery, using the guide wire to guide it. A balloon-carrying catheter is then fed through the guide catheter, also using the guide wire as a guide. The guide catheter is then advanced to a preselected point so that its distal end is downstream of the stenotic lesion, and the balloon catheter is positioned so that the balloon is in registration with said lesion, also known as a stenosis. The guide catheter is withdrawn a relatively short distance to expose the balloon catheter. The balloon is then inflated to permanently dilate and tear the two inner layers of the artery, thereby enlarging its diameter, breaking up the stenosis, thereby increasing the blood-carrying capacity of the artery. An expandable stent may be carried on the outer surface of the balloon and left in place after the balloon is deflated and withdrawn. Alternatively, a self-expanding stent may be deployed over the treated lesion using a different delivery catheter. The stent holds the arterial walls in their expanded condition. After the balloon is deflated, the balloon catheter is withdrawn into the guide catheter, and both of said catheters and the guide wire are withdrawn to conclude the procedure.
The primary drawback to balloon angioplasty or stenting is the creation of debris and thrombus that can clog blood vessels downstream of the treatment site. The stretching of the two inner arterial walls breaks up the stenotic lesion and creates debris known as emboli. Accordingly, when the balloon is deflated, the emboli flow downstream with the blood. If the stenotic lesion is in the iliac or femoral arteries, the emboli may flow to the feet; this may or may not be problematic. However, if the stenotic lesion is in the carotid artery, the emboli can flow into various brain vessels and cause permanent brain damage. Similarly, kidney damage can ensue from dilating a lesion in the main renal artery. For this reason, balloon angioplasty carries a higher risk of embolic complications for stenotic lesions in the carotid, renal, and coronary arteries unless means are provided for preventing the flow of emboli to the blood vessels of the brain, kidney, or heart, respectively.
U.S. Pat. No. 5,833,644 discloses a complex catheter system that deploys at least two additional balloons that flank the main balloon that stretches the blood vessel. When inflated, the auxiliary balloons isolate the treatment area so that emboli cannot flow therefrom. However, no blood can flow to the brain when the auxiliary balloons are inflated, so the physician must perform the treatment in an expedited manner to avoid brain damage arising from oxygen deprivation. This can result in less than optimal treatment. Catheters of this type also include dedicated lumens for aspiration and irrigation and may require a complex electromechanical system to operate and control the saline flow rate, pressure, and the like.
PCT patent application No. PCT/US98/01894 filed by Yadav, published Aug. 6, 1998, discloses an emboli-catching device that is mounted to the distal end of a guidewire. It is positioned downstream of the stenotic lesion and opened up, much like an umbrella, to catch the emboli created by inflation of the angioplasty balloon. It is designed for use in the carotid artery and is formed of a material that is permeable to red blood cells so the brain is not deprived of oxygen during its deployment. However, since it must be positioned downstream of the stenotic lesion, it cannot be used in the lower half of the body because such use would require that it be fed to its operative location from a point in the upper half of the body. Moreover, the mechanism required to deploy and retract the emboli-catching means requires a dedicated sheath which makes the procedure relatively complex.
Several prior art emboli-catching devices also rely upon mesh-carrying frames that are formed of a flexible and resilient material such as a nickel-titanium alloy. The problem with such devices is that they pop open when they emerge from a containment catheter. Some of them spring open under their inherent bias until they hit the interior walls of an artery, and others spring open to a predetermined diameter that may be less than the diameter of an artery. In either case, the physician cannot instantaneously control the amount of opening or closing of the mesh. In other words, the nickel-titanium devices are either fully open or fully closed and the physician cannot open or close such devices to an infinite plurality of functional positions of adjustment because the opening or closing of the emboli-catching device is not under the positive control of the physician.
What is needed, then, is an emboli containment and removal device that does not block blood flow when in use, which can be used with any diagnosis or treatment catheter, which is small, which is mechanically simple in construction, and which is under the positive control of the physician. Moreover, such a device is needed that can be used in the carotid artery and in other blood vessels, including those in the region of the kidneys, heart, and peripheral blood vessels.
However, it was not obvious to those of ordinary skill in this art how the needed improvements could be provided, in view of the art considered as a whole at the time the present invention was made.
The long-standing but heretofore unfulfilled need for an innovation that overcomes the limitations of the prior art is now met by a new, useful, and nonobvious invention. A first embodiment of the novel apparatus for performing balloon angioplasty and/or stenting includes a guide wire of elongate, flexible construction and a balloon catheter that slideably receives the guide wire. A plurality of longitudinally disposed, circumferentially spaced apart jointed members is formed in the balloon catheter near a distal end thereof. Each joint member of the plurality of joint members has a proximal joint, a distal joint longitudinally spaced apart from the proximal joint, and a middle joint that is substantially half-way between the proximal and distal joints. The jointed members have a position of repose where no bends are formed in any of the joints and the jointed members are therefore substantially flush with the exterior cylindrical wall of the balloon catheter. Each middle joint is displaced radially outwardly, with respect to a longitudinal axis of the balloon catheter, when the distance between its associated proximal and distal joints is reduced, and each middle joint is displaced radially inwardly when that distance is increased. A first displacement means is provided for selectively displacing each of the distal joints toward their associated proximal joints, and a second displacement means is provided for displacing each of the distal joints away from their associated proximal joints to return the jointed members to their position of repose. Both displacement means are under the positive control of a physician and the amount of displacement can be any amount so that the joint members have an infinite number of positions of functional adjustment.
A mesh structure of flexible construction has a generally frusto-conical configuration when in repose and is disposed in partially ensleeving relation to the balloon catheter. More particularly, in a first configuration, a first relatively short distal extent of the mesh structure is secured to the balloon catheter distally of the jointed members and a second predetermined proximal extent of the mesh structure ensleeves about half the extent of the jointed members. Thus, the proximal end of the mesh structure is enlarged in diameter when the middle joints are displaced radially outwardly. However, as will become clear as this disclosure continues, the just-described configuration of the mesh structure may be reversed so that the proximal end of the mesh structure is secured to the balloon catheter, proximally of the jointed members, and the distal end thereof is disposed in partially ensleeving relation to the jointed members so that the distal end of the mesh structure is enlarged when the middle joints are displaced radially outwardly. This enables the novel structure to be positioned downstream of a stenosis whether it is positioned in an artery where blood is flowing upwardly or downwardly with respect to the heart.
The mesh structure allows blood to flow therethrough and captures and retains emboli produced by a balloon angioplasty and/or stenting procedure when the middle joints are displaced radially outwardly. The mesh structure returns to its position of repose when the middle joints are displaced radially inwardly.
Significantly, the jointed members do not deploy automatically under the influence of shape memory when released from the confines of the guide catheter or other catheter which contains them; the deployment is under the control of a physician. Similarly, the return to said position of repose is not a result of the resiliency of the materials of which the balloon and/or stenting catheter and jointed members are made. Instead, the above-mentioned second displacement means is a guide catheter that is displaced by a physician in a proximal-to-distal direction to cause the collapse of the jointed members, it being understood that said guide catheter ensleeves the balloon and/or stenting catheter.
A nickel-titanium alloy is the preferred material of which the jointed members are made. Such an alloy is a shape memory alloy, but the memory is insufficient to cause full deployment of the mesh structure when the guide catheter is withdrawn in a distal-to-proximal direction to expose the balloon and the jointed members. Moreover, by employing the first and second displacement means, both of which are under the positive control of a physician, as the positive means for opening and closing said jointed members, respectively, there is no need to use an enhanced shape memory alloy such as a stress-induced martensite alloy as disclosed and broadly claimed in U.S. Pat. No. 5,067,957. Such shape memory alloys are not under the positive control of a physician in that they spring open to their maximum diameter when released from a containment catheter and thus cannot fulfill an important object of this invention.
The first displacement means is advantageously provided in the form of a stop means carried by the guide wire near a distal end thereof. The stop means has a breadth greater than the interior diameter of the balloon catheter. Accordingly, an initial displacement of the guide wire in a distal-to-proximal direction, by a physician, causes the stop means to abut a distal end of the balloon catheter and continued displacement causes the middle joints to displace radially outwardly. This enables the physician to open the jointed members to any percentage of full opening as may be desired.
The stop means is preferably provided in the form of a bead that is formed on the guide wire near its distal end. The bead has a diameter greater than the internal diameter of the balloon catheter; preferably, the bead diameter is greater than the internal diameter of the distal tip of said balloon catheter.
The mesh structure has a generally frusto-conical shape when the middle joint members are radially deployed. A first end of the mesh structure has a first diameter, a second end has a diameter greater than the first diameter, and a generally conical body extends between the first and second ends. The diameter of the second end spans the lumen of the artery within which the novel balloon catheter is deployed so that all emboli produced by the treatment procedure are captured in the mesh.
In a second embodiment, the novel jointed members are formed in a catheter, sometimes known as an inner catheter, that is received within the balloon catheter. Due to the small diameter of the inner catheter, it may be enlarged in the region of the jointed members to facilitate their construction. However, if the inner catheter is formed of a suitable material, the enlarged part is not needed.
In a third embodiment, the novel jointed members are formed in a guidewire of the type having a coiled outer sheath and an elongate rod slideably mounted therein. The opening and closing of the jointed members is under the positive control of a physician because the physician controls the instantaneous position of the elongate rod.
It is a primary object of this invention to provide an emboli collector suitable for use in any part of the body, whether in a region where blood flows upwardly or downwardly with respect to the heart.
Another important object is to provide an emboli collector that is opened and closed by positive displacement means under the positive control of a physician so that said opening and closing is not dependent upon the use of special alloys having a shape memory.
Still another important object is to provide an emboli collector that may be formed in a balloon catheter, in an inner lumen, or in a guidewire.
Another object is to provide an emboli collector having a mechanically simple structure.
These and other important objects, features, and advantages of the invention will become apparent as this description proceeds.
The invention accordingly comprises the features of construction, combination of elements and arrangement of parts that will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.